The present invention relates to a spring system for delaying the action for pistol-caliber firearms with blowback action.
Blowback loaders use the energy from the recoil to open the chamber after a shot, eject the cartridge shell, and feed a new cartridge from the magazine into the chamber. Different action types with their advantages and disadvantages have been developed over the course of time. In principle, a distinction is made between two types—unlocked blowback action and locked recoil action. In both types, the chamber is opened only when the projectile has left the barrel and the gas pressure has decreased to a non-critical value.
For the blowback action, also called spring-mass bolt action, the barrel and bolt are not connected to each other mechanically; the bolt acts only through its mass inertia and through the pressure of the closing spring. The bolt sits directly behind the cartridge chamber and presses on the base of the cartridge. The bolt is held, in turn, by the closing spring that is supported on the weapon's housing.
After the propellant charge is ignited, a high gas pressure occurs in the interior of the cartridge shell; this pressure sets the projectile in motion toward the front of the weapon and the bolt in motion toward the back. The speed of the bolt must remain low enough that the cartridge shell slides backward in the chamber only a short distance while the pressure in its interior is so high that it could cause damage or injury. This is achieved in that the mass of the bolt is significantly greater than that of the mass of the projectile. Ideally, an identical motion impulse is transferred to the projectile and to the bolt during a shot. According to the law of conservation of momentum, in the much heavier bolt, this impulse leads to a significantly lower velocity.
After the projectile has left the barrel, the bolt continues to move backward due to its mass inertia, wherein the cartridge shell is pushed out completely from the cartridge chamber and ejected. The stored spring energy increases as the compression of the spring increases. When the bolt has discharged all its kinetic energy to the spring or impacts against a stop and in this way comes to be in its rear dead point, it is accelerated forward again by the spring, wherein a new cartridge is guided out of the magazine into the cartridge chamber.
In weapons with delayed blowback action, the barrel sits rigidly in the housing and is locked semi-rigidly with the bolt. The bolt has two parts; at the front, the bolt head is connected movably to the control piece. The pressure produced during a shot on the end side of the bolt head causes minimal backward movement. This movement is transferred by a suitable mechanism to the control piece and greatly accelerates this piece. During blowback, the control piece releases the locking of the bolt head and moves with the bolt head backward, which triggers the reloading process.